In preparing the coating compositions referred to in the Abstract (see U.S. Pat. No. 4,164,487), amines other than triethylamine can be employed. In any case, however, it is highly desirable to introduce the amine in excess of the amount required to salify enough of the P--OH groups in the reaction product to render it dispersible in water. Thus, the overhead formed by boiling off the reaction medium only not includes water but also the excess amine--which must be recovered--for both economic and environmental reasons.
In most methods of amine extraction found in the literature, the amine component of a fluid stream is adsorbed on a solid. Adsorption on activated carbon, for example, is essentially irreversible but reversible adsorption occurs when the solid is an ion-exchange resin (as described by B. S. Fee and M. G. Rogers; Separation of Amines by Ligand Exchange; Parts I-IV. Analytica Chimica Acta; 32 (1965) p. 101, 33 (1965) pp. 84-90, and 37 (1967), pp. 102-111). No disclosure of liquid/liquid amine extraction or of simultaneously extracting more than incidental amounts of water was found in the literature.
Triethylamine is preferred for other reasons in the manufacture of the above-referred-to coating compositions and, fortunately, has proven to be particularly amenable to recovery by the process of the present invention.
The only references found to uses of triethylamine phosphate salts are in U.S. Pat. No. 2,917,481--which discloses the use of such salts as corrosion inhibitors--and in U.S. Pat. No. 3,300,693, which is directed to the use of quaternary ammonium salts as dielectric fluids.